Centenary Bulletin 20 – Coopers Filters Abergavenny, UK
February 13, 2019
Just before Forest and Construction Equipment was formed, Norman G Clark became the Australian agent for Coopers Filters, and on the formation of FCE used this company as the vehicle for all the selling and promotion of the Cooper product.
Cooper Filters, of Abergavenny in Wales, was the largest manufacturer of air filters in the UK, and had a very large business in Europe. They supplied air filters for practically everything that moved under its own power.
In their range was a very special filter system, which was marketed under the trade name of Cooper King. There were several models that made it possible to fit most diesels in the high-power range of construction machinery.
The special feature of Cooper King was that it was a range of self-cleaning filters matching that of the market leading Donaldson product. The significant difference was that the Cooper King was designed to operate as a single element system with no pre-cleaner.
The filter element was quite expensive and made from very high quality woollen Barathea fabric of billiard table felt standard. This was a more effective filtering material than the regular paper elements used in all other high-grade air filters around the world.
The self-cleaning feature was also of great interest, as filter elements in construction machines usually have a very short life due to operating in dusty conditions, and require regular replacement at considerable expense.
The Cooper King filter kit came complete with a compressed air bottle, and it required an air supply to operate the self-cleaning feature.
Inside the filter itself, was a rotary segment which controlled an air divider. At rest, the divider covered one eighth of the total circumference of the inside of the filter element. The machines compressed air system was connected to the Cooper King blast bottle through a flow control valve. The bottle pressure was built up to about 100PSI over a period of approximately one minute. At 100 PSI an exhaust valve tripped, and a blast of high-pressure air was directed through the air divider to one eighth of the inside of the filter element, blowing the accumulated dust out of the element. When all air was exhausted from the bottle, the air divider indexed one eighth of a turn and the blast bottle started to build up pressure again ready for the next sector to be cleaned.
It was a great idea, and it really worked. A lot of contractors fitted the system to their machines, as it was a much better option than regular air filter maintenance which was always expensive, and prone to allowing dust into the engine during the service.
We were getting very good feedback on the product until a problem arose from a rear engine scraper operating in northern Western Australia. The operator had “dusted” the engine because the filter had allowed dust to pass. It was assumed that the installation had probably been at fault, and at no time did anyone claim there was any defect in the Cooper King system.
Sometime later we sold three very big loaders to BHP Whyalla, which were quoted with Cooper King filters. When it came to delivery, BHP decided to fit only one with a Cooper King for evaluation, and the others to be standard filters.
Just as well, as the machines were constantly monitored by oil sampling for engine wear, and after about six months, it was obvious that the Cooper King installation was letting dust through. This time there was no doubt the Cooper King was at fault.
It was agreed with BHP that there was no point rebuilding the engine at this stage, and it could continue until a major overhaul. We were allowed to run an installation and operations check, and to make regular checks on the amount of dust inside the inlet manifold. This routine confirmed that there was dust passing the filter element even though there was nothing wrong with the installation or the operation of the system.
We removed the elements and fitted new ones and sent the originals back to England for evaluation. They tested 100% efficient, but something was very wrong.
What was showing up were some very funny facts that did not make sense. If the weather was hot there was dust in the inlet manifold. If it was cold there wasn’t, but we didn’t have an explanation.
Flying back from Whyalla to Melbourne one night, the penny dropped, and it was all so obvious. Whyalla was a very hot and dry place, and in the Iron Knob mine at the loading face, temperatures would frequently exceed 45 degree centigrade for days on end. Relative humidity would also be close to zero. In addition, the air cleaners were mounted on the engine fire wall, and even in reasonably moderate temperatures, the metal would be much too hot to touch.
The very dry environment of Whyalla had caused the natural woollen fibres to shrink, thus, allowing the fine mesh opening to enlarge and allowing the fine dust of the mine through into the engine. Coopers, on testing, could find nothing wrong with the filter mesh count. Undoubtedly, they would have taken the best part of week in transit from the hot Whyalla environment to the very gentle climate of Abergavenny. The wool fibre would rapidly soak up its lost moisture and return the fabric structure to normal.
The manufacturer had every right to claim that there was nothing wrong with the elements returned from Whyalla.
Our previous experience with Drytester, in the textile industry, confirmed our suspicions. The fabric was simply over dried, and the weave hole size would have expanded due to yarn shrinkage. We contacted Drytester who confirmed that the fabric structure had changed, and after making a calculation, they believed that the hole size could have been as much as 42% bigger.
Sometimes at Whyalla they would have a cold day, or even a shower of rain, and the wool would almost immediately return to its natural moisture condition. On such occasions, there was no evidence of dust in the engine manifold.
We now knew why the filter was allowing dust through to the engine, but there wasn’t an easy fix. The Cooper King filter needed a robust filter fabric to withstand the cleaning blast which only a woollen filter could provide.
There was no solution so, reluctantly, we stopped selling Cooper King filters, as they did not work in extremely hot, dry conditions.
Fifteen years later we were contacted by a customer looking for a new element for his Cooper King filter. The unit he was talking about was one we had fitted to a Michigan loader, that was sold by FCE. It had been working in Gippsland for nearly 15 years, and during that period the filter never put a foot wrong.
There is no doubt that the Cooper King was really a great product. It had never been tested in the harsh environment of Australian mining operations, and without the former association with Drytester, it is probable that no one would ever know why the system had not worked in the BHP application. It was a great pity that we were not able to solve the low humidity problem.